Re: [IRCA] Craig Barnes' 3.5 inch Baby FSL Rocks at Rockwork

[Guy Atkins <dx@xxxxxxxxxxxxx>]

Gary, you described the effort very well. Seattle DXer Chuck Hutton and
Andy Ikin (Wellbrook Communications) were also involved in the discussion
on how to successfully make an FSL broadband in reception.

I thought I had success with a FLG100 module as an interface when the combo
provided weak audio on 738 kHz Tahiti (when they were still on the air)
from suburban Puyallup, WA. Later tests right at the coast however showed
the supposed "broadband" FSL to be a very mediocre performer. My guess is
that Tahiti was propagating extra well that night into Puyallup, enabling
reception even on the altered FSL antenna. (This arrangement had the wire
ends of the FSL coil directly attached to the input of the Wellbrook
FLG100, no variable capacitor used).

I'm sure it would be much easier to achieve good, *single-frequency*
reception with a FSL antenna and SDR radio (or other 50-ohms receiver for
that matter). There are different approaches to coupling coils and
impedance matching on the web--check out this link for instance:
https://www.nonstopsystems.com/radio/frank_radio_antenna_magloop.htm
This wouldn't be much different than coupling coils for air core box loops,
feeding a receiver. After the discouragement with the broadband efforts I
didn't pursue single frequency FSL reception.

Also, Everett Sharp tried coupling coils with FSLs. If I remember
correctly, he posted in the Ultralight Radio group that he had gotten best
performance with a 64:1 ratio of transformer between the coupling coil and
50-ohms antenna input.

73,

Guy Atkins
Puyallup, WA



---------- Forwarded message ----------
> From: Gary DeBock <d1028gary@xxxxxxxxxxx>
> To: Rick Kunath <k9ao@xxxxxxxxx>, "Rick Kunath' via NRC-AM" <
> nrc-am@xxxxxxxxxxxxxxxx>
> Cc: "America, Mailing" <irca@xxxxxxxxxxxxxxxx>
> Bcc:
> Date: Wed, 22 Aug 2018 13:57:09 -0700 (PDT)
> Subject: Re: [IRCA] [nrc-am] Craig Barnes' 3.5 inch Baby FSL Rocks at
> Rockwork
> Hi Rick,
>
> <<< Has anyone done any experiments with an inductive secondary coupling
> loop on an FSL or a high-impedance unity gain preamp with an unbalanced low
> impedance output across the loop winding? I.e. what would be needed to
> couple to a receiver or an SDR? >>>
>
> Local buddy Guy Atkins (also living here in Puyallup) has performed
> multiple experiments attempting to match the compact gain performance of
> the FSL antenna with the Perseus-SDR receiver, and back in 2013 Guy tried
> almost every conceivable interface (low-noise Wellbrook preamps, sensing
> coils, direct connections, etc.) in order to somehow match the
> single-optimized-frequency performance of the FSL with the state-of-the-art
> Perseus-SDR receiver. Because of intense interest among local broadband
> DXers over $1K was used in these experiments, which unfortunately ran into
> the stark reality that a high-Q, single-optimized-frequency antenna with
> razor-sharp tuning peaks is not very compatible with a spectrum capture
> receiver requiring a broadband antenna to record all MW frequencies
> simultaneously. That's not to say that the FSL antenna couldn't be used on
> single frequencies to provide exceptional gain for the Perseus-SDR (or
> other 50 ohm antenna input receivers) once an impedance-matching system is
> devised, and I'm pretty sure that Guy experimented with those type of
> matching systems, and how to get good performance on narrow frequency
> ranges with a Perseus + FSL combination. But the essential fact remains
> that almost all Perseus-SDR DXers are oriented toward spectrum capture of
> the entire MW frequency range, and will not be satisfied with exceptional
> antenna performance on one single frequency.
>
> 73, Gary DeBock (in Puyallup, WA, USA)
>
>
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